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Forecasting the flood

Water is released from the Jamestown Reservoir as seen Thursday. The National Weather Service regional flood forecast was released Thursday. Forecasts from the U.S. Army Corps of Engineers may be released next week. John M. Steiner / The Sun

Officials are gaining confidence in the river level forecasts for this spring on the James River and Pipestem Creek, according to Allen Schlag, hydrologist with the National Weather Service in Bismarck.

Forecasts for releases from the Jamestown and Pipestem dams are anticipated next week from the U.S. Army Corps of Engineers. Those forecasts will determine the river levels, and if dikes will be necessary, in Jamestown, according to Jerry Bergquist, Stutsman County emergency manager.

"We're starting to get a good grasp at what we're looking at," Schlag said. "It's not so preliminary now; we're close enough to the spring melt."

The latest information from aerial surveys in the northern portions of the watersheds was surprising, Schlag said.

"North of Jamestown, the numbers actually went up," he said, referring to the amount of moisture in the snowpack. "The latest flights came back with higher numbers than before."

Forecasts for Pipestem Creek near Pingree indicate a 10 percent to 20 percent chance of minor flooding from March 25 to April 22. Minor flooding at Pingree is a river level of more than 11 feet. Pipestem Creek is currently at 4.8 feet. The Pipestem Creek forecast for the Pingree area does not include any chance of moderate or major flooding.

The peak forecast for the James River near Grace City occurs during the week of April 8. At that time, the river has about a 25 percent chance of topping the bridge over the river south of town.

The forecast indicates at least a 25 percent chance of moderate flooding at Grace City during the weeks of March 18 and March 25. There is a 30 percent to 40 percent chance of major flooding during the weeks of April 1 and April 8.

Moderate flooding at Grace City would be a river level of 14 feet with major flooding occurring at 15 feet. The James River at Grace City is currently at 4.5 feet.

Downstream, the James River at LaMoure has between a 10 percent and 20 percent chance of reaching minor flood stage between April 15 and May 6. Minor flood stage at LaMoure is 14 feet with the river currently at 7 1/2 feet.

In Jamestown, releases from the dams and river levels are likely to rise but possibly not to a level requiring the construction of temporary dikes, Berquist said. Temporary dikes were constructed in Jamestown in 2009 and 2011 to prevent damage from high releases from the dams.

Schlag said the flood forecasts are based on normal precipitation through May 13, although he doesn't anticipate major adjustments.

"Even above normal precipitation won't double the amount of moisture on the ground (this late in the winter)," he said, referring to future flood forecasts.

Bergquist said there are still a lot of unknowns regarding the possibility of spring flooding this year.

"That's a good thing," he said. "In 2009, by this time we already knew we were having a flood."

The next river forecast from the National Weather Service is planned for March 2.

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